Monitoring foods to be eaten occurs by means of the chemical senses. The sense of taste is little understood at the biochemical level, and the mechanisms by which taste receptors discriminate among various types of stimulus molecules have yet to be explained. This program is a study of the biochemical basis of taste, focusing on mechanisms of recognition of taste stimuli at the molecular level. This approach to investigate taste is based on measuring the direct interactions (binding) of radioactively-labeled or fluorescent taste stimuli to various types of preparation from taste tissue. For example, binding of radioactively-labeled chemostimulatory amino acids is measured to a plasma-membrane containing fraction from the taste tissue of the catfish Ictalurus punctatus. Interactions of taste stimuli with plasma membranes are being used to define the characteristics of the recognition of taste stimulus molecules by their receptor sites. BIBLIOGRAPHIC REFERENCES: Cagan, R.H. Biochemical Studies of Taste Sensation II. Labeling of Cyclic AMP of Bovine Taste Papillae in Response to Sweet and Bitter Stimuli. J. Neurosci. Res. 2 (1976). Brand, J.G. and Cagan, R.H. Biochemical Studies of Taste Sensation III. Preparation of a Suspension of Bovine Taste Bud Cells and Their Labeling with a Fluorescent Probe. J. Neurobiol. 7, 205-220 (1976).